Machines such as, for example, dozers, loaders, excavators, motor graders, and other types of heavy equipment use hydraulic actuators coupled to a work implement for manipulation of a load. Such machines generally do not include shock absorbing systems and, thus, may pitch, lope, or bounce upon encountering uneven or rough terrain. The substantial inertia of the work implement and associated load tends to exacerbate these movements, resulting in increased wear of the machine and discomfort for the operator.
One method of reducing the magnitude of the movements attributable to the work implement and associated load is described in U.S. Pat. No. 7,194,856 (the '856 patent) issued to Ma et al. on Mar. 27, 2007. The '856 patent describes a machine hydraulic system having a reservoir configured to hold a supply of fluid, a source of pressurized fluid, and an actuator situated to move an implement of the machine. A plurality of valves are disposed between the actuator and the reservoir and source to regulate flows of fluid to and from the actuator to move the actuator and connected implement. The hydraulic system also includes an accumulator selectively communicated with the actuator to cushion movement of the actuator and implement.
The accumulator of the '856 patent can be communicated with the actuator to cushion movements of the implement when a ride control mode of operation is activated. The ride control mode of operation can either be manually activated or automatically activated in response to one or more input. For example, a button, switch, or other operator control device may be associated with an operator station of the machine and, when manually engaged by an operator, the operator control device can cause the ride control mode of operation to be activated. Conversely, a controller may receive input indicative of a travel speed of the machine, a loading condition of the machine, a position or orientation of the implement, or other such input, and automatically enter the ride control mode of operation based on the input.
Although the ride control system of the '856 patent may reduce undesired movements of a machine's implement, it may be less than optimal. Specifically, the hydraulic system of the '856 patent may be caused to enter and exit the ride control mode of operation too often. As a result, components of the hydraulic system may wear prematurely.
The disclosed hydraulic system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.